AN ABSTRACT OF THE THESES OF
Joseph T. Lipka IC
Geology
for the degree of Master of Science in
presented on
April 17, 1987
Title: STRATIGRAPHY AND STRUCTURE OF THE SOUTHERN SULPHUR
SPRING RANGE, EUREKA COUNTY, NEVADA
Abstract approved:
Redacted for Privacy
G. Johnson
U
Early Paleozoic limestones and dolomites of the shallow shelf
transitional facies belt were mapped in the southern Sulphur Spring
Range, Eureka County, Nevada. The four youngest units in the map area
are in fault contact with the Lower Devonian rocks and were probably
transported westward, along a low-angle normal fault.
The minoirlal dolomites of the Hanson Creek Formation, dated as
latest Ordovician in the map area, were deposited in a low-energy
lagoon.
Overlying the Hanson Creek Formation, with a gradational
contact, is the lower member of the Lone Mountain Dolomite, a probable
reef complex. The exposed thickness of the lower Lone Mountain
Dolomite is estimated to be 250 feet. The Lower Devonian Old Whalen
Member of the Lone Mountain Dolomite is composed of well-bedded,
alternating brown and gray dolomites. The repetition of rock types in
the Old Whalen Member indicates recurring shallow marine environments
on a broad carbonate platform. The Old Whalen is estimated to be 1400
feet thick. Directly overlying the Old Whalen Member, is the Kobeh
Member of the Mc Colley Canyon Formation.
Rocks of the Mc Colley Canyon
Formation were deposited on a shallow shelf under normal marine
conditions.
The mid-Lower Devonian Kobeh Member is sparsely to
abundantly fosciliferous and varies from a peloidal wackestone to a
peloidal sandy wackestone to a sandy peloidal packstone. The
thickness is 276 feet. Overlying the Kobeh Member are the abundantly
fossiliferous beds of the lower part of the Bartine. Member.
The lower
part of the Bartine ranges from a wackestone to a packstone and
weathers to a chacteristic yellowish tan. The upper part of the
Bartine varies from wackestone to packstone, is darker in color, and
is sparsely to moderately fcssiliferous. The thickness of the Bartine
Member is 189 feet, and it is late Early Devonian in age. The Sadler
Ranch Formation is a dolomitic wackestone containing crinoids with or
without brachiopods, and it is latest Early Devonian in age. The
Sadler Ranch Formation was deposited on a shallow shelf under normal
marine conditions. Above the Sadler Ranch Formation is the lower
member of the Oxyoke Canyon Sandstone. The lower member of the Oxyoke
varies from a peloidal packstone to sandy peloidal wackestone to
quartzite. The upper member of the Oxyoke Canyon Sandstone is a
structureless dolomitic mixlstone. The Oxyoke Canyon Sandstone was
probably deposited in a high to moderate energy lagoon with a
subsequent decrease in depositional energy. The Middle Devonian
Sentinel Mountain Dolomite overlies the Oxyoke Canyon Sandstone.
The
Sentinel Mountain is a structureless to finely laminated dolomite that
was deposited in a lagoon that initially had open circulation, but
which was later cut off. The youngest formation in the map area is
the Permian Garden Valley Formation which is a reddish brown
silicified conglomerate.
The Sadler Ranch Formation, Oxyoke Canyon Sandstone, Sentinel
Mountain Dolomite, and Garden Valley Formation are all present as
allochthonous blacks, which were transported from the east as a result
of movement along low-angle normal faults. The Nooks were juxtaposed
on top of the autochthonous Old Whalen Member of the Lone Mountain
Dolomite and on the McColley Canyon Formation. Denudation of the
Kobeh and Bartine Members of the McColley Canyon Formation occurred as
a reguili- of the movement on the faults. The timing of the movement on
the low-angle normal faults is Estimated to be Cretaceous because of
the eastern source and the pre-Cretaceous age of the allochthonous
rocks. The age is still problematical as a consequence of the lack of
any cross-cutting dikes or other age-determinable units.
Stratigraphy and Structure
of the
Southern Sulphur Spring Range
Eureka County, Nevada
by
Joseph T. Lip Ica II
A THESES
submitted to
Oregon State University
in partial fulfillment of
the requirements for the
degree of
Master of Science
Completed April 17, 1987
Commencement June 1987
APPROVED:
Redacted for Privacy
Pfe4)or of Geoloizain charge of major
Redacted for Privacy
Departmen
Geology
Redacted for Privacy
Dean of Grad
School
(
Date thesis is present&
Typed by
Joseph T. Lipka II
April 17, 1987
ACKNOWLEDGEMENTS
At the ere of a movie one often sees the credit "...and a cast of
thousands". In the case of a thesis, especially this thesis, the more
appropriate credit reads "...and a cast of several". I would now like
to thank, in writing, those very important "several".
Many thanks go to Dr. Johnson, who let me join the team in the
middle of the season. Dr. "J" devised the thesis project, are made
are (in his unique way) that the project was finished. I wish to
thank Lynne Lipka, who also happens to be my wife, for all kinds of
stuff.
Claudia Regier skillfully picked the conodonts, a thankless
task until now. A well thought thank you to the Friday afternoon "T"
group, which proved every week that you can get a bunch of geologists
together and not once will they even mention geology. Thanks to Mr.
Stephen Sans for letting me use his magic machine, without the machine
I would still be writing the introduction. A big thank you to my
parents, Joseph and Carmen, or as I call them Dad and Mom. I also
wish to acknowledge the financial support of Amerada Hess Corporation,
Amoco Production Company, Marathon Oil Company, and Mobil Oil
Corporation. Last and certainly not least I would like to thank the
little fuzzy people, Winky "aunt bubba" and Mauly.
TABLE OF CONTENTS
INTRODUCTION
1
Purpose
1
Location and description
2
Methods
2
Terminology
5
Previous work
6
Geologic setting
7
HANSON CREEK FORMATION
12
General statement
12
Litho logy and age
13
Contacts and thickness
14
LONE MOUNTAIN DOLOMITE
16
General statement
16
Lone Mountain Dolomite, lower member
17
Lone Mountain Dolomite, Old Whalen Member
20
MCCOLLEY CANYON FORMATION
28
General statement
28
Kobeh Member
29
Bartine Member, lower part
37
Bartine Member, upper part
41
SADLER RANCH FORMATION
44
General statement
44
Litho logy and age
44
OXYOKE CANYON SANDSTONE
48
General statement
48
Oxyoke Canyon Sandstone, lower member
50
Oxyoke Canyon Sandstone, upper member
54
SENTINEL MOUNTAIN DOLOMITE
57
General statement
57
Litho logy and outcrop chacteristics
58
Contacts and age
60
GARDEN VALLEY FORMATION
61
DEPOSITIONAL HISTORY
63
STRUCTURE
73
Cretaceous? low-angle normal faults
73
Tertiary normal faults
80
CONCLUSIONS
81
REFERENCES
84
APPENDIX
88
Faunal lists aryl localities
88
LIST OF FIGURES
Figure
1
Page
Index map of Nevada, showing counties and area
of figure 2.
2
Index map of central Nevada, showing thesis
3
Contact between the brown dolomite and the gray
4
dolomite of the Old Whalen Member of the Lone
Mountain Dolomite. Bailey Pass, northern portion
of the map area
4
21
Northern boundary of the map area, showing the
contact between the Old Whalen Member of the Lone
Mountain Dolomite, and the Kobeh Member of the
Mc Colley Canyon Formation.
5
27
Typical outcrop of the Kobeh Member of the Mc Colley
Canyon Formation. Mulligan Gap area.
30
Figure
6
Page
Weathered surface of Kobeh Member wackestone,
which contains silicified corals
7
Slabbed sample of wackestone from the Kobeh
Member, McColley Canyon Formation.
8
34
Photomicrograph of peloidal sandy wackestone,
Kobeh Member of the McColley Canyon Formation.
9
33
36
Hand sample of the brachiopod and trilobite
packstone from the lower part of the Bartine
Member of the Mc Colley Canyon Formation.
10
Slabbed sample of the crinoidal dolomite from the
Saal Pr Ranch Formation.
11
42
45
Outcrop photograph of the lower member of the
Oxyoke Canyon Sandstone and the underlying
lower part of the Bartine Member of the Mc Colley
Canyon Formation.
Mulligan Gap area near JL-129.
49
Page
Figure
12
Cross-lamination in the lower member of the
Oxyoke Canyon Sandstone.
13
Hand sample of the reddish brown silicified
conglomerate from the Garden Valley Formation.
14
62
Present juxtaposition of formations in the
southern Sulphur Spring Range.
15
51
75
Correlation chart for part of the Lower and
Midge Devonian.
76
LIST OF PLATES
Plate
1
Geologic Map of the Southern Sulphur Spring Range,
Eureka County, Nevada
2
.in pocket
Geologic Cram-sections of the Southern Sulphur
Spring Range, Eureka County, Nevada
.in pocket
3
Mulligan Gap I measured section.
.in pocket
4
Mulligan Gap IC measured section.
.in pocket
STRATLGRAPHY AND STRUCTURE
OF THE SOUTHERN SULPHUR SPRING RANGE,
EUREKA COUNTY, NEVADA
INTRODUCTION
Purpose
The purpose of this project has been to study, characterize, and
map the early Paleozoic rock units in the southern Sulphur Spring
Range, Eureka County, Nevada.
A second objective was to study the
stratigraphy and structure of the rock units and attempt to determine
the depositional environments and relationships to the regional
paleogeography.
A third objective was to obtain conodont and
brachiopod data for time correlation of the rock units and to aid in
the determination of their depositional environments.
2
Location and Description
The map area encompasses the southern quarter of the Sulphur
Spring Range.
The area is represented on the U.S. Geological Survey
Garden Valley 15-minute topographic quadrangle map, which is located
approximately 15 'rules northwest of Eureka, Nevada (see Figures 1 and
2).
Access to the map area is via unimproved roads which lead off of
a county road along the eastern margin of the range.
Methods
A total of 10 weeks were spent in the field during the fall of
1984 and the summer of 1985. Fieldwork involved mapping Paleozoic
units, collecting samples for lithologic and paleontologic study, and
measuring and describing sections. Studies of lithology were aided by
petrographic examination of representative thin sections. Selected
samples were slabbed in order to examine bedding features.
Samples ranging from 10 to 20 pounds were collected in the field
for the purpose of obtaining conodonts and brachiopods. Conodont
3
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Figure 1. Index map of Nevada.
showing counties and
area of Figure 2.
LINCOLN
4
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* Battle Mountain
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Figure 2. Index map of central Nevada, showing
thesis area.
5
samples were prepared by first dissolving the crushed rock material in
10 % formic acid.
The insoluhlp residue was then separated in heavy
liquid (tetrabromoethane). The conodonts were then hand picked and
placed on slides by Claudia Kegler. Dr. Gilbert K]apper, University
of Iowa, made the identifications and age determinations of the
conodonts.
The undissolved residue from the conodont extraction was
the primary source for silicified brachiopods. The non-silicified
brachiopods were obtained by breaking up the sample in a hydraulic
rock-splitter. The cleaned brachiopods were submitted to Dr. J. G.
Johnson, Oregon State University, for identification and age
determination. A sample of Lower Devonian corals was submitted to Dr.
William A. Oliver Jr., U.S. Geological Survey, for identification and
age determination.
Terminology
The carbonate clacification of Dunham (1962) was used for hand
sample and thin - section description.
Folk's 1965 crystal size designation was used to describe the
recrystallized carbonates. The designations are as follows:
<0.004
mm aphanocrystalline, 0.004 to 0.016 mm very finely crystalline,
6
0.016 to 0.062 mm finely crystalline, 0.062 to 0.25 mm medium
crystalline, 0.25 to 1.0 mm coarsely crystalline, and 1.0 to 4.0 mm is
very coarsely crystalline. The same designations were used to
describe the sizes of microscopic quartz grains and crinoid columnals
present in the thin sections.
Rock colors were determined by comparison with the Rock-Color
Chart published by the Geological Society of America (1963).
Previous Work
In the vicinity of the map area, four previous studies have been
completed.
Carlisle et al. (1957) studied the Devonian stratigraphy
in the Sulphur Spring and Pinyon Ranges. Kendall (1975) did an M.S.
thesis study of Lower and Middle Devonian strata in the central and
northern portions of the Sulphur Spring Range, as part of a
county-wide investigation.
Colman (1979) studied the petrology and
biostratigraphy of the Old Whalen Member of the Lone Mountain
Dolomite in the range as a thesis project
7
Geologic Setting
At the present-day site of the Great Basin, shallow water
sediments were deposited in a westward-thickening wedge from the late
Precambrian (approximately 850 Ma.) to the early Paleozoic. This
wedge, part of the Cordilleran geosyncline, extended from southern
California to the Canadian Arctic (Roberts, 1972) and was the dominant
geological feature in eastern, central, and southern Nevada until the
middle Paleozoic (Stewart, 1980).
In central Nevada, the deposition of shallow water
miogeosynclinal sediments, began in the Cambrian, and continued into
Ordovician time.
Four Ordovician depositional provinces are
recognized, from east to west: 1) a carbonate and quartzite province,
2) a shale and limestone province, 3) a shale and chert province, and
4) a chert-shale-quartzite-greenstone province (Stewart, 1980). The
Hanson Creek Formation, which in the study area is latest Ordovician
and Silurian in age, is within the carbonate and quartzite province.
This province is characterized by deposition in lagoons and on shoals
(Dunham, 1977; Stewart, 1980).
8
The Silurian was a continuation of the shallow water shelf
deposition in the miogeosyncline.
This system is the most limited
areally and the thinnest of any lower or middle Paleozoic system in
Nevada.
However, four depositional provinces are recognized, from
east to west: 1) a dolomite province, 2) a laminated limestone
province, 3) a chert and shale province, and 4) a feldspathic
sandstone province (Stewart, 1980). The Lone Mountain Dolomite is
within the dolomite province.
Rocks in the dolomite province are
almost entirely gray, thin- to thick-bedded, with a few dark gray,
locally cherty units (Matti and Mckee, 1977; Nichols and Silber ling,
1977; Stewart, 1980).
The earlier sedimentary pattern of shallow water deposition in
the miogeosynclinal belt to the west, and deeper-water deposition
farther west persisted into the Late Devonian. Again, four
depositional provinces are recognized: 1) a carbonate and quartzite
province, 2) a limestone and shale province, 3) a shale and chert
province, and 4) a chert province.
Rocks of the southern Sulphur
Spring Range are within the carbonate and quartzite as well as the
limestone and shale provinces. Those of the carbonate and quartzite
province are cliff-forming, thin- to thick-bedded limestones and
dolomites, some of which contain quartzose sandy and silty units and
9
interbedded sandstones or quartzites. These units are primarily
shallow water subtidal, intertidal, and supratidal sediments formed
on a broad inner shelf (Stewart, 1980).
The Old Whalen Member of the
Lone Mountain Dolomite, the Sadler Ran Ch Formation, the Oxyoke Canyon
Formation, and the Sentinel Mountain Dolomite are units exposed in the
field area. Collectively, they have depositional characteristics
indicative of the carbonate and quartzite province. According to
Stewart (1980) rocks of the limestone and shale provinces were
deposited in moderately deep water near the outer edge of the shelf.
However, depositional textures present in the Kobeh and Bartine
Formations of the Sulphur Spring Range indicate a shallow-subtirlal
environment of deposition.
During the Late Devonian, the pattern of sedimentation changed
with the onset of the Antler orogeny. The Late Devonian to Early
Mimissippian Antler orogeny produced the Roberts Mountains thrust in
which rocks of the deep water siliceous and volcanic assemblages were
thrust eastward over shallow water and related rocks. The Sulphur
Spring Range lies at the leading or eastern edge of the thrust
(Stewart, 1980). The Antler orogeny formed a highland extending from
southwestern to northern Nevada and beyond. Detrital material eroded
10
from the Antler belt, formed thick accumulations of sediment during
Miszissippian time in an adjacent foreland basin to the east.
This pattern of sedimentation, which began in the Mississppian,
continued into the Permian.
Within Nevada, five major depositional
provinces of Permian rocks are recognized. They are from east to
west: 1) carbonate, sandstone, and siltstone province in cratonal and
rniogeosynclinal areas in eastern Nevada, 2) carbonate-tenigenous
detrital province east of the Antler highland, 3) conglomerate and
carbonate province within the Antler highland, 4) rocks of an
allochthonous,
siliceous, and volcanic province within and west of
the Antler highland, and 5) volcanic province in westernmcst Nevada.
Those of the carbonate- terrigenous province contain abundant
silirlagtic detrital material shed eastward from the Antler highland.
In the Sulphur Spring Range, the Garden Valley Formation is included
in the carbonate-terrigenous detrital province (Stewart, 1980).
The Sonoma orogeny took place during Late Permian to the Early
Triassic time.
This deformation resulted in the eastward movement of
ocean-floor sediments over the shallow water deposits of the Antler
highland (Stewart, 1980). The Sevier orogeny followed, with
deformation beginning in the Early Cretaceous and lasting until
Campanian time.
Most of Nevada was in the hinterland of the Sevier
orogenic belt (Armstrong, 1968).
11
The next major geologic event was defined by crustal extension
during the Cenozoic, which produced the present-day block-faulted
basins and ranges (Stewart, 1980).
12
HANSON CREEK FORMATION
General Statement
The oldest unit mapped in the study area is the Ordovician and
Silurian Hanson Creek Formation. This formation crops out in the
southeastern portion of the map area, on the west side of an
east-dipping fault block (see Plate 1). The Hanson Creek Formation
was defined by Merriam (1940) along Pete Hanson Creek in the Roberts
Mountains.
Merriam described the unit as lying between the Eureka
Quartzite and a black chert zone.
The black chert zone became the
base for the Roberts Mountains Formation, which Merriam also described
in 1940.
Roberts et al.. (1967) described the Hanson Creek Formation
as being a dark gray to black, thick-bedded, coarse-grained dolomite
which is more thinly bedded toward the top.
13
Litho logy And Age
The Hanson Creek Formation, in the southern Sulphur Spring Range,
is a finely crystalline dolomite. On weathered surfaces the rocks are
a brownish gray where as on fresh surfaces they are dark brownish
gray.
The unit has undulatory bedding-plane partings at 6 inch to 1
foot intervals. The dolomite is fetid and contains abundant veinlets
of calcite. The Hanson Creek Formation is moderately foesW.ferous
with silicified crinoids and crinoid fragments being the only
macrofossils.
The crinoirls are round and very fine- to fine-grained
in size. The unit also contains abundant elongate chert nodules,
which average three inches in length. In outcrop, the Hanson Creek
appears very similar to the Devonian Old Whalen Member of the Lone
Mountain Dolomite.
However, it is not as well-bedded as the Old
Whalen and also contains abundant chert nodules and crinoiris.
In thin section, the Hanson Creek Formation is seen to be
composed of finely crystalline dolomite; the boundaries of the
crystals are well defined. The dolomite is cloudy because of
disseminated organic matter, which is present both at grain boundaries
and inside the dolomite crystals,
Fossil material, primarily crinoid
14
columnals, constitute 10 % of the total rock. Ghosts of crinoid
columnals are present and display a sub-parallel alignment. Aside
from the sub-parallel alignment of the crinoid ghosts, the rock is
homogeneous.
Porosity is appoximately 10 % and is present as
irregularly shaped vugs or fractures that have been partially infilled
with dolomite, or calcite.
The Hanson Creek Formation was dated on the basis of conodonts.
One sample was assigned to the ordovicius Zone, which is in the
uppermost part of the Ordovician (Klapper, written communication,
1985).
Elsewhere, the upper Hanson Creek has been dated as early
Silurian (Murphy et aL, 1979).
Contacts And Thickness
The most extensive outcrop of Hanson Creek Formation is found
along the west side of an east-dipping fault block. This fault block
also contains exposures of the Lone Mountain Dolomite. The contact
between the two units is gradational over an interval of approximately
150 feet; from the brownish gray dolomite of the Hanson Creek to the
white to light gray of the Lone Mountain Dolomite.
The Hanson Creek
15
Formation where faulted, is defined by extensive shearing and the
presence of brecciated dolomite and silica coated slickensides.
The
shearing is most evident in the fault block adjacent to the main
Hanson Creek outcrop (see Plate 1). Across the western fault is the
down-dropped Old Whalen Member of the Lone Mountain Dolomite.
Because the lower contact for the Hanson Creek Formation is not
exposed, it was not possible to determine the thickness for the unit.
16
LONE MOUNTAIN DOLOMITE
General Statement
The Lone Moutain Dolomite was named by Hague in 1892, for
exposures at Lone Mountain.
The unit was defined as the Paleozoic
strata lying between the Eureka Quartzite and the Nevada Limestone.
Merriam, in 1940, redefined Hague's Lone Mountain to include only the
strata between the Roberts Mountains Formation (described by Merriam
in 1940) and the overlying Devonian Nevada Formation.
Meniam's
(1940) Lone Mountain Dolomite at Lone Mountain is 1570 feet thick.
The lower 1170 feet are light gray massive dolomite; the upper 400
feet consist of alternating bands of light and dark dolomite.
Nichols and SUberling (1977) divided the Lone Mountain Dolomite into
two units in the Roberts Mountains.
Colman (1979), in the Sulphur Spring Range, studied the petrology
and biostratigraphy of the Old Whalen Member, the uppermost of three
informal members of the Lone Mountain Dolomite. Colman divided the
17
Old Whalen Member into two major lithologic groups, each with
three subdivisions. The two major lithologic groups are brown
dolomite and gray dolomite.
As not
by Colman, the subdivisions are
oonsidered to be representative end members. Of the three
subdivisions in the brown and gray dolomite, four were found in the
study area. They are: brown peloidal dolomite and brown skeletal
fragment dolomite, along with gray laminated dolomite and gray
peloidal dolomite.
Lone Mountain Dolomite, lower member
The lower Lone Mountain Dolomite crops out as a prominent ridge
along the southeast flank of the range (see Plate 1). The unit lies
in a fault block together with the Hanson Creek Formation. The
dolomite is white to light gray to medium light gray on weathered
surfaces. Fresh surfaces are light gray to light brownish gray.
The
Lone Mountain Dolomite, as described by Nichols and Silberling (1977)
is a secondary dolomite in which the rock is replaced or further
alt -erred after deposition and is generally chacterized by a sugary
recrystallized texture. The coarser crystalline Lone Mountain has
this sugary texture and nowhere were any primary textures observed.
18
The unit has bedding plane partings spaced 1 to 4 feet.
Within the
dolomite and throughout the formation are breccia beds which are 1 to
3 feet thick. The breccia has undergone extensive alteration,
probably in the telogenic and mesogenic zone, as indicated by the
abundant calcite veins, which have destroyed the original fabric of
the rock.
In thin section, the Lone Mountain Dolomite displays a variance
in crystal size from the northern to the southern outcrops. The
dolomite in the southern outcrop area tends to be very finely
crystalline. In the central and northern parts the crystals range
from fine to coarsely crystalline, with medium crystals the most
abundant. The coarser crystalline dolomite displays a sharp gradation
of crystal sizes. Over an interval of approximately 30 mm, the
dolomite changes from fine to medium to coarsely crystalline. The
boundaries between the different crystal sizes are sharp. The texture
of fine to coarsely crystalline dolomite tends to be equant within
each size grouping
In two samples a stylolite is present at the
boundary. Porosity ranges from 1 to 5% and is in the form of
irregularly shaped vugs and fractures. The vugs throughout the unit
are infilled with dolomite or calcite. The vugs to the south are
infilled with dolomite and chalcedony. In the central and northern
19
areas the vugs are infilled with coarsely crystalline pseudospar or
have been enlarged by dissolution. A sample from the north shows a
solution breccia.
The lower Lone Mountain Dolomite overlies the Hanson Creek
Formation with a gradational contact (see Hanson Creek Formation
section) over approximately 150 stratigraphic feet. The Lone Mountain
is in fault contact with the uppermost member, the Old Whalen, and the
Kobeh Member of the Mc Colley Canyon Formation (see Plates 1, and 2).
The exposed incomplete thickness of the lower Lone Mountain is
estimated to be 250 feet. The age could not be determined in the study
area because of a lack of observed fossils.
20
Lone Mountain Dolomite, Old Whalen Member
The Old Whalen Member of the Lone Mountain Dolomite is the unit
with the greatest areal extent in the map area (see Plate 1). The Old
Whalen is composed of alternating, well-bedded, dark brownish gray
dolomites and medium gray dolomites. The dark brownish gray dolomite
weathers to a brownish gray; the medium gray dolomite weathers to a
light gray. The contact between the gray dolomite and brown dolomite
tends to be sharp, though some gradation does exist where brown
dolomite overlies gray dolomite (see Figure 3). The Old Whalen is a
very distinctive unit in the field because of the regular "stair-step"
outcrop pattern. The dolomite forms benches which range in thickness
from 1 to 6 feet and which are spaced 20 to 60 feet apart. Bedding
plane partings occur at 2 to 4 foot intervals. Both the brown and
gray dolomite appear blocky in outcrop as the rocks exhibit a
columnar-like jointing pattern. Overall, the brown dolomite tends to
be finely laminated and fetid while the gray dolomite tends to be
structurelem and not fetid.
In hand sample, the brown dolomite appears finely laminated,
convolute laminated, with some samples containing abundant
21
Figure 3.
Contact between the brown dolomite and the gray dolomite
of the Old Whalen Member of the Lone Mountain Dolomite.
Bailey Pam, northern protion of map area.
22
macrofossiLs.
The gray dolomite is finely, and irregularly laminated.
The gray dolomite forms the largest outcrops in the map area. The
outcrops are cliffs that range from 30 to 60 feet in height.
Brecciation is pervasive in the Old Whalen Member. Most brecciation
is probably related to faulting because the dolomite appears to be
fractured, with the fractures thrilled with calcite. Observed in the
vicinity of the breccias are slickensides, some coated with calcite,
others with silica. The fault breccias crop out as 1 to 2 foot thick
by 10 to 20 foot long "beds" which are perpendicular to strike.
An
intraformational breccia was found in the northwest portion of the map
area. The angular clasts, which range from <1 inch to 3 inches in
diameter, are primarily dark brownish gray dolomite; the matrix is
composed of medium gray dolomite.
In thin section, two types of brown dolomite and two types of
gray dolomite are described. 'The brown dolomites are the brown
peloidal dolomite and the brown skeletal fragment dolomite. The gray
dolomites are the gray laminated dolomite and the gray peLoidal
dolomite.
The dolomite types are those described by Colman (1979).
Two samples of breccia are also described.
The brown peloidal dolomite is composed of dolomite crystals
0.016 to 0.062 mm in diameter, or fine to medium crystalline with the
23
average being 0.039 mm. The boundaries of the crystals appear to be
slightly leached as the edges of the crystals are irregular or are
indistinct. The unit is composed of approximately 80 % dolomite.
Organic material is pervasive and gives the crystals a cloudy
appearance.
Peloirls represent 30% of the rock. The peloids vary from
ovoid to elongate pellets which are approximately 0.008 mm in diameter
to indeterminate lumps or patch. All of the peloids are evenly
distributed. Some of the lumps are ovoid in shape, but are not of a
consistent size. Most of the peloids have indistinct boundaries or
are themselves indistinct, probably a result of dolomitization.
Porosity in the dolomite is in the form of fenestrae, fractures, and
irregularly shaped vugs.
The pores have been infilled with dolomite
crystals which range in size from fine to coarse.
The brown skeletal fragment dolomite is composed of dolomite
crystals 0.004 to 0.062 mm in diameter with an average of 0.016 mm or
finely crystalline. The crystals are equant in texture and the
boundaries are slightly leached. The fossil fragments, which compose
approximately 40 % of the total rock, are primarily whole or fragmented
rugose corals and crinoid fragments in matrix support. The fossil
fragments contain medium-sized dolomite crystals (0.25 to 0.062 mm in
diameter).
The long axes of the fmcils display a subparallel
24
alignment. Porosity is approximately 10 % and is intraparticle (the
inside of the corals) or as fractures, both of which are partially
infilled with dolomite.
The gray laminated dolomite is composed of dolomite crystals
<0.004 mm in diameter. The boundaries of the visible dolomite
crystals are irregular and extensively leached. Laminations are 1 to
2 mm thick and show significant displacment by fractures. In thin
section, the dolomite is seen to be composed of approximately 20%
peloids and <5% fossil fragments. The peloids range from 0.004 to
0.016 mm in diameter and are probably pellets which have been
subsequently dolomitized. The fossil fragments identified were
gastropods and trilobites
The dolomite contains a few stylalites.
Porosity is 25% and in the form of fractures which have been partially
infilled with very fine (0.004 to 0.016 mm in diameter) or coarsely
crystalline (0.25 to 1.0 mm) dolomite.
The other type of gray dolomite found is a peicidai dolomite.
The dolomite contains pellets which range from 0.08 to 0.25 mm and
are ovoid to elongate. The pellets compose 10 % of the total rock and
are evenly distributed.
Pellets in the sample are similar in
appearance to the pellets found in the Kcbeh Member of the Mc Colley
Canyon Formation.
The orientation of the pellets produces a crude
25
lamination.
The dolomite is composed of dolomite crystals which range
from <0.004 to 0.016 mm in diameter and which are equant. Porosity
was estimated to be approximately 20%. The porosity is in the form of
fractures and fenestrae, both of which are partially filled with
dolomite.
The infilling dolomite crystals range from 0.016 to 0.25 mm
in diameter.
The breccia samples studied are probably intraformational
breccias. The clasts are in matrix support.
Casts are angular to
subrounded and appear to be similar to the dolomites found in the rest
of the member. Clact sizes range from 0.008 to 5.0 mm in diameter.
The matrix is composed of <0.004 mm dolomite crystals. The clasts are
fractured and some contain irregularly shaped vugs. Both the
fractures and vugs are infilled with dolomite. The other breccia
sample is composed of angular clasts of sandy peloidal packstone to
grainstone. The quartz grains are subangular to subrounded, 0.016 to
0.062 mm in diameter, and compose 30 % of the clasts. Another 30% of
the clasts are peloids, which are ovoid in shape though some have been
squashed.
They appear to have been composed of organic and miciitic
material, which has subsequently been recrystallized.
26
The lower contact of the Old Whalen Member is covered by
undifferentiated Quaternary alluvium. In the southwest portion of the
map area, a normal fault separates the Old Whalen from the underlying
Lone Mountain Dolomite and Hanson Creek Formation.
On the west side
of the study area, the Old Whalen is separated from the Permian Garden
Valley Formation by a north-south-trending normal fault, which extends
the length of the map (see Plate 1). The contact with the overlying
Kobeh Member of the McCulley Canyon Formation is sharp (see Figure 4),
with an abrupt change in color and outcrop characteristics (see Kobeh
Member section).
Between the two units, the contact is not observed
because of the bench or "stair-step" outcrop pattern of the Old
Whalen.
The first Kobeh bed is set back from the 'last- Old Whalen bed
by 20 to 60 feet, with the interval between the two covered.
The lower contact of the Old Whalen is not exposed, but the
estimated maximum exposed thickness is approximately 1400 feet.
A conodont sample (JL-74) was obtained from the Old Whalen Member
in the central portion of the map area. The sample indicates an
Early Devonian age (Mapper, written communication, 1985).
27
Figure 4.
Northern boundary of the map area, showing the contact
between the Old Whalen Member of the Lone Mountain
Dolomite (background, right), and the Kobeh Member of
the McC alley Canyon Formation (background, left, and
foreground). Note that the vegetation limit
approximately fnllnws the contact. Also note the
bedding of the Old Whalen Member.
28
MCCOLLEY CANYON FORMATION
General Statement
Overlying the Old Whalen Member of the Lone Mountain Dolomite is
the Mc Colley Canyon Formation. The rocks of the Mc Colley Canyon
Formation were originally part of the Nevada Limestone of Hague
(1883).
Merriam (1940) redefined and restricted the Nevada Formation
to include the strata above the Lone Mountain Dolomite and below the
Devils Gate Limestone.
CarliAlp et al. (1957), working in the Sulphur
Spring and Pinyon Ranges, subdivided the Nevada Formation into three
members. In ascending order they are: the Mc Colley Canyon Member,
the Union Mountain Member, and the Tel
Canyon Member. Johnson
(1962) recognized an abrupt faunal. and Ethological change at the top
of the Mc Colley Canyon Member.
This break was interpreted to be an
unconformity and warranted elevating the McColley Canyon Member to
formational status.
Gronberg (1967) proposed a three-fold subdivision
of the Mc Colley Canyon Formation. In ascending order they are: the
Kobeh Member, the Bartine Member, and the Coils Creek Member.
29
Murphy and Gronberg (1970) proposed the three as formal members. In
the map area the Mc Colley Canyon Formation is represented by only the
Kobeh and Bartine Members.
Kobeh Member
Directly overlying the Old Whalen Member of the Lone Mountain
Dolomite is the Kobeh Member of the Mc Colley Canyon Formation. Rarely
was a bed-on-bed contact observed,. because of the "st-air-step" outcrop
characteristic of the Old Whalen. The Kobeh Member does not form
well - defined "stair-step" bedding like the Old Whalen Member.
The
Kobeh is only fair to poorly bedded with bedding thickness ranging
from 1 to 3 feet (see Figure 5). The poor bedding, limestone
lithology, and fossil content of the Kobeh make for a distinct
contact. The thickness of the Kobeh, as measured at the Mulligan Gap
I section, is 276 feet (see Plate 3). The Kobeh weathers to a medium
light gray to light gray, with fresh surfaces a medium gray to brown
gray. In hand sample, the Kobeh appears to be a sandy wackestone or
packstone; in thin section, the unit is seen to contain abundant
peloids as well as sand grains.
30
Figure 5.
Typical outcrop of the Robeh Member of the Mc Colley
Canyon Formation. Mulligan Gap area.
31'
Above the Old Whalen Member, the Kobeh first appears either as a
light gray dolomite with sparse orinoicl fragments (see Plate 3) or as
a peloidal sandy wackestone. The typical thickness of the dolomite
beds is five feet.
However, in the southern portion of the map area, the Kobeh has
been dolornitized far upsection from the Old Whalen-Kobeh contact.
This is probably a secondary dolomitization, perhaps related to
hydrothermal activity in the mesogenetic zone (Nichols and Silber ling,
1977).
The section of Kobeh that was dolomitized has been repeated by
normal faulting; this was discovered by conodont age dating.
Above
the pPloidal wackestone, the Kcbeh ranges from a peloidal sandy
wackestone or packstone to a peloirisl sandy packstone. The Kcbeh
Member is sparsely to moderately fossiliferous at the top and base,
and moderately to abundantly fossiliferous in the middle.
In thin section, the Kobeh Member consists of peloirls which range
from 10 to 70% of the total rock. Pe kid sizes range from 0.008 to
0.5 mm in diameter, the average being 0.016 mm. The peloids are
elongate to ovoid and are, as a rule, evenly distirbuted throughout
the rock. Because of the uniform shape and size of the peloids, they
are probably fecal pellets.
32
All of the samples contain quartz grains. Quartz content varies
from 5 to 30% of the total rock. The grains are similar to the
pellets in size, ranging from 0.008 to 0.5 mm in diameter. They are
angular to subrounded and have irregular boundaries indicating
leaching. Some of the grains have overgrowths.
Fossils and fossil fragments range from 5 to 50% of the
allochems.
Dimarticulated acinoids as well as fragmented crinoirls
are the most abundant fossil type. Fragmented trilobites,
brachiopods, rugose corals, bryozoans, gastropods, and mollusks are
also found in the unit (see Figure 6, and 7). Asa rule, if only one
type of fossil is present it is crinoids, which are generally
fragmented.
Although ciinoias are the dominant fossil type, in
individual samples trilobites, brachiopods, or bryozoans can dominate.
In the packstones the long axes of the fossil fragments display a
subparallel alignment. In the wackestones the fossils are randomly
oriented and distributed.
Porosity ranges from <1 to 20% with 5% the average. The
porosity is in the form of fractures, some of which have been
partially infilled with pseudospar; one sample has the fractures
infilled with silica. Samples with corals and bryozoans tend to have
intraparticle porosity, infilled with pseudospar or silica.
33
Figure 6.
Weathered surface of Kobeh Member wackestone, which
contains silicified corals. Note that the corals
display a positive relief.
34
Figure 7.
Slabbed sample of wackestone from the Kobeh Member,
Mc Colley Canyon Formation.
and lower right of the sample.
Note the large corals in the upper left
35
One sample, a peloidal wackestone from the top of the member,
contains mudstone interbeds 2 to 3 mm thick.
Organic matter is found
primarily in the pellets, which are dispersed throughout the rock.
The pellets display varying degrees of compaction; some are flattened,
others are elongated. In some samples they are ovoid.
In some samples bioturbation appears pervasive, based on the lack
of laminae and the even distribution of the peloids. One sample
(JL-94) contains vertical burrows filled with micrite, but no pellets
or fossil material
That sample also displays a fining upward grading
of fossil fragments. In JL-116, the pellets define the laminae, which
are approximately 2 mm thick. The fossil material has been
recrystalli zed to pseudospar or microspar. Sample JL-65, a peloidal
packstone, contains a gastropod infilled with micrite, along with
trilobite and brachiopod fragments (see Figure 8). The inside of the
gastropod contains a few pellets.
The age of the Kobeh Member was determined by utilizing both
conodonts and brachiopods. The conodonts obtained from the Kobeh
range from the ml.catus Zone to the
communication, 1985).
brachiopod samples
kind & Zone (Mapper, written
These zones are of mice -Early Devonian age. The
belong
to the Spinoplmia Zone anterval 5 or 6)
and the kobehana Zone anberwa 8 or 9). Both the
Spinoplasia Zone
and the kobehana Zone fall within the Pragian Stage of the
Devonian (Johnson, 1977).
Lower
36
L
/ mm
Figure 8.
Photomicrograph of peloirial sandy wackestone, Kobeh
Member of the Mc Colley Canyon Formation. Note the
trilobite fragment in the center of .the photo is within
a large gastropod shell, which has been filled with
micrite.
37
Bartine Member, lower part
Overlying the Kobeh Member are the abundantly fossiliferous beds
of the lower part of the Bartine Member. The contact between the two
members is obscured at most places by scree from the overlying Oxyoke
Canyon Formation.
Where the contact is seen it is poorly exposed
because of the recessive nature of both the Bartine and Kobeh, but
especially the Bartine. The transition from Kobeh to Bartine is
characterized by the appearance of yellowish tan soils and abundant
silicified brachiopods, some of which have weathered free.
The lower
Bartine weathers as small plates 3 to 5 inches across and 0.5 to 2
inches thick. The plates vary from the distinctive yellowish tan to
various shades of orange. The color of fresh surfaces is medium gray
to yellowish gray. Outcrops of the Bartine are found in only one
location in the map area, approximately 0.5 miles south of Mulligan
Gap.
Bedding is very poorly developed, but where seen is 1 to 2.5
feet thick. The thickness of the Bartine, measured at the Mulligan
Gap I section, is 183 feet (see Plate 3). This is an estimated
thickness because of the lack of outcrops.
38
Even though outcrops are rare, three distinct nth:Logics are
evident in the lower Bartine. The are: a sparsely to abundantly
fossiliferous (brachiopod) wackestone, a transitional fades, and an
abundantly fossiliferous packstone. In hand sample, the wackestone is
composed of whale brachiopods which have been aligned so that the long
axes parallel the crude bedding.
The packstone, in hand specimen,
contains abundant brachiopods and trilobites nested to form a fossil
hash (see Figure 9). The brachiopods are found whole, disarticulated,
and fragmented. The trilobites are found disarticulated or as
fragments.
The intermediate fades is transitional between the
wackestone and the packstone.
In thin section, the brachiopod wackestone is seen to be composed
of 60% fossil material. Along with the brachiopods, which are whale
or disarticulated, the rock contains disarticulated trilobites, whole
gastropods, and other mollusks. The fossils display a weak parallel
alignment and have been recryst-alli zed to microspar. Porosity is
approximately 1% and is in the form of fractures partially infilled
with pseudospar.
The packstone is seen in thin section to be a sandy peloidal
packstone to a peloidal brachiopod wackestone. The peloidal
39
Figure 9.
Hand sample of the brachiopod and trilobite packstone of
the lower part of the Bartine Member of the Mc Colley
Canyon Formation.
40
brachiopod wackestone is composed of 80 % allochems, of which 45% are
fossils and 55% are peloids. The fossils are whale brachiopods,
disarticulated trilobites, and whale to fragmented gastropods. The
fossils display a parallel alignment of the long axes and all are
oriented concave down. Showing no alignment, the peloids average
0.008 mm in diameter and are elongate to ovoid. The peloids are
uniform in size and shape and are probably fecal pellets. They appear
to be completely mientized.
Within the fossil layers are very thin
micrite beds which contain the pellets. The sample contains what
appear to be branching burrows and blebs of micrite with few, if any,
pellets.
Porosity is very low in the sample (<5%) and is in the form
of secondary intraparticle porosity in some of the brachiopods.
Fractures present are infilled with pseudospar.
The sandy peloidal wackestone is composed of 30 % quartz grains
and 50 % all.ochems (the remaining 20 % is micrite), of which 20% is
fossil fragments and 80 % is peloids. The quartz grains are angular
and average 0.008 mm in diameter, and display undulatory extinction.
The peloids also average 0.008 mm in diameter and are elongate to
ovoid.
pmloitis.
Uniform size and shape indicate a fecal pellet origin for the
Fossils present in the sample are disarticulated brachiopods
and trilobites. Where there are fossil fragments present in the
sample there tend to be very few or no quartz grains present. As in
the other lower Bartine samples, the sandy pekidal wackstone also
41
displays a parallel orientation of the long axes of fossils. The
brachiopods and trilobites have been infilled with authigenic
chalcedony.
Porosity is approximately 20 % and is in the form of
fractures, and irregularly shaped vugs, which are partially infilled
with pseudospar. There is some interparticle porosity, which has been
infilled with chalcedony.
Bartine Member, upper part
The upper portion of the Bartine is different from the lower in
two aspects. First, the upper unit weathers to a medium light gray
with fresh surfaces a medium gray. Second, the upper unit is a
sparsely to moderately fossiliferous wackestone overlain by a
moderately fossiliferous packstone. Individual beds range from 1 to 3
inches thick. The packstone contains quartz grains and lithoclasts.
The fossil material in both lithologies is primarily arinoirls,
predominantly represented by doilhip ossicks. The fossils are
oriented parallel to the bedding.
42
The succession of lithologies within the upper Bartine is more
complex than described above. The wackestone and packstone units are
underlain and overlain by thin (1 to 2 inch thick) breccia beds. The
breccia beds appear to be composed of wackestone and packstone. The
upper packstone is separated from the wackestone by a thin (1 to 2.5
inch thick) mudstone bed. Bedding in the upper unit is fairly well
developed compared to the poorly developed bedding in the lower
Bartine.
The upper unit is exposed at only one location (JL-123),
approximately two miles south of Mulligan Gap (see Plate 1).
The
outcrop is only 6 feet thick and approximately 20 to 30 feet wide,
therefore it was not mapped as a separate unit. The upper unit is
overlain by the lower unit of the Oxyoke Canyon Formation. A
low-angle normal fault delineates the contact.
In thin section, the crinoicial wackestone is found to contain
c:dnoic3s1 packstone lithoclasts.
The rock has a jumbled appearance.
The crinoids are disarticulated and are severely leached, some so much
that identification is difficult. The crinoids are randomly
distributed and oriented. The sample studied is composed of 55%
allochems, of which 80 % are crinoids and 20 % are peloids.
Some
43
.of the crinoids are of the doithle ossicle variety. The peloids
average 0.008 mm in diameter, are ovoid, and completely micritized;
they are possibly fecal pellets. The crinoidal packstone lithoclasts
are up to 3 mm in diameter and are rounded. The unit contains angular
quartz grains similar to those found throughout the area, but they
make up only about 1% of the rock.
Very little organic matter is
present, and that is scattered. Porosity is approximately 10 % and is
in the form of fractures and irregularly shaped vugs. The vugs are
partially infilled with pseudospar and the fractures are partially
infilled with chalcedony.
The Bartine Member was age-dated utilizing both conodonts and
brachiopods.
The conodonts obtained from the Bartine range from the
dehiscens Zone to the inversus Zone (Mapper, written
communication, 1985).
The brachiopods obtained are from the
pinyonensis Zone anterval 10 or 11), which is within the Emsian
(Johnson, written communication, 1985.). The above data indicate a
late Early Devonian age for the Bartine.
The conodonts obtained from
the upper part (JL-123) are within the inversus Zone (Klapper,
written communication, 1985).
44
SADLER RANCH FORMAI:10N
General Statement
The first of the allochthonous blocks described in the map area
is the Sadler Ranch Formation. Kendall (1975) first described the
formation, with the type section located west of the Sadler Ranch in
the central Sulphur Spring Range. The formation was originally the
middle or crinoidal unit of the Union Mountain Member of Carlisle et
al. (1957).
Kendall (1975) was able to discern three units within the
formation:
a lower dolomite, a middle crinoidal dolomite, and an
upper dolomite. Became the Sadler Ranch Formation occurs as
allochthonous blocks in the map area, only an incomplete section was
found.
The rocks that make up the allochthonous blocks are part of
the middle crinoidal dolomite (see Figure 10).
Litho logy And Age
The Sadler Ranch Formation is light gray to light brownish gray
45
Figure 10.
Slabbed sample of the crinoidal dolomite from the Sadler
Ranch Formation. Note the double ossicle crinoiris in
the upper left and center of the sample
46
on weathered surfaces.
gray.
Fresh surfaces are medium gray to brownish
The lithology varies from a dolomitic crinaidal wackestone to a
dolomitic crinoid-brachiopod wackestone.
The dolomitic crinnirlal-brachiopod wackestone alternates with two
inch thick, well-bedded dolomitic mudstone and dolomitic silty
mudstone.
There is also a dolomitic ccinoirlal packstone.
The
contacts between the units are sharp and undulatory. All the
dolomites are fetid on a fresh break. Bedding plane partings occur at
one to six foot intervals. The crinoids and the other fossil
fragments are calcareous and in some beds display a subparallel
orientation.
Most of the crinoids are very distinct because they have
doithlP cesicles.
The double-ossicle crinaids are found in only one
other unit, the upper part of the Bartine Member.
The Sadler Ranch Formation samples studied in thin section are of
the dolomitic crinoirlal wackestone. The unit contains approximately
30 % cclumnals, which are composed of calcite. The crinoirls are
randomly distributed and oriented throughout the sample.
Approximately 20 % of the total rock is composed of angular to
subrounded, very fine-grained quartz. The dolomite crystals range
from aphanocrystalline to finely crystalline.
is estimated to be 80 %.
The amount of dolomite
The crystals have irregular boundaries and
are cloudy; most are leached.
47
The conodonts which date the Sadler Ranch Formation range from
the serotinus Zone to the patiilns Zone (Klapper, written
communication, 1985).
Devonian.
This places the formation in the late Early
The age determination in the map area for the Sad Pr Ranch
Formation correlates with the conodont--baesd dates obtained by Kendall
et at (1983).
48
OXYOKE CANYON SANDSTONE
General Statement
The Oxyoke Canyon Sandstone is one of the five units that Nolan
et al_ defined in 1956. They described it as composed of fine- to
medium-grained, rounded quartz in a dolomitic matrix.
They also
reported that where faulting had occurred the Oxyoke Canyon Sandstone
became vitreous and quartzitic. Hose et al. (1982) raised the Oxyoke
Canyon Sandstone to formational status. The Oxyoke Canyon Sandstone
variously overlies the Bartine (see Figure 11) and Kobeh members of
the McCulley Canyon Formation, and the Old Whalen Member of the Lone
Mountain Dolomite (see Plate 2). The contact is a low-angle normal
fault and is obscured at most places by scree from the very resistant
Oxyoke Canyon Sandstone. The most visible contact is the sharp Oxyoke
Canyon-Kobeh contact.
The upper unit of the Oxyoke Canyon Sandstone
overlies the lower unit of the Oxyoke with a gradational contact over
an interval of tens of feet, in the southern map area. The Sentinel
Mountain Dolomite overlies only the lower unit of the Oxyoke Canyon
Formation (see Plate 2, section A -A).
49
Figure 11.
Outcrop photograph of the lower member of the Oxyoke
Canyon Sandstone (background) and the underlying lower
part of the Bartine Member of the Mc Colley Canyon
Formation (foreground). Note that the hat is resting on
the top of the Bartine Member bed. Mulligan Gap area,
near JL-129.
50
The Oxyoke Canyon Formation and the Sentinel Mountain Dolomite
are both allochthonous units which were brought into the area by
movement along low-angle normal faults. A low-angle normal fault
separates the Oxyoke Canyon from the overlying Sentinel Mountain
Dolomite. In the central map area the upper unit is separated from
the lower unit by a 6 inch chert bed. This is probably a fault plane.
Oxyoke Canyon Sandstone, lower member
The lower Oxyoke in hand specimen appears to be a very fine- to
medium-grained, moderately well sorted sandstone with subrounded to
rounded grains. However, in thin section the composition of the lower
part of the Oxyoke Canyon is not so simple. The lower unit in the
Oxyoke Canyon Formation varies from a peloidal packstone to a sandy
peloidal wackestone, both of which have been dolomitized, to a
quartzite.
The color on fresh surfaces is white to light gray.
Weathered
surfaces are light red, light brown, medium gray, or light brownish
gray.
The lower Oxyoke is commonly iron-stained. Finely laminated at
the base, the member becomes cross-laminated upsection (see Figure
51
Figure 12.
Cross-lamination in the lower member of the Oxyoke
Canyon Sandstone.
52
12), and then again finely laminated. The sets of the cross strata
range from three to twelve inches thick. The lower Oxyoke Canyon
crops out as cliffs from five to one hundred feet high. The lower unit
is best exposed in the Mulligan Gap area and just south of JL-123.
The lower Oxyoke Canyon is probably the most resistant unit in the
study area. This is exemplified by the presence of the unit on the
tops of the hills where it acts as a cap, protecting the less
resistant units below, i.e. the Bartine and Kobeh Members.
Also, many
small landslide blocks of the lower unit are seen down slope from the
main outcrops (see Plate 1). Because the lower unit is so resistant
the underlying units tend to be buried by the scree derived from the
lower Oxyoke.
Most Bartine Member exposures are completely covered by
the scree. A sample of the lower unit was dated with conodonts. The
sample yielded Icriodus sp. indef.. (Klapper, written communication,
1985) which indicates a Devonian age for the unit. The significance
of the Devonian age is that on lithologic criteria the lower Oxyoke,
especially the quartzite at the top of the range, can be confused with
the Eureka Quartzite, which is widespread throughout the county.
In thin section, the peloidal packstone is seen to be composed
almost entirely of pellets; 90 % of the allochems are pellets and 90 %
of the rock is made up of allochems.
There is some fossil material
53
present that is identifiable as fragmented crinoids. In addition, 1%
of the rock is angular, very fine quartz. The matrix has been
dolomitized, with the crystals ranging from <0.004 to 0.016 mm in
diameter. The peloids, which average 0.008 mm in diameter and are
elongate to ovoid, probably are fecal pellets which have been
completely micritized.
mm thick.
The unit is laminated with laminae one to two
The crinoirls and the other fossil material have the long
axes oriented parallel to the laminae. Interparticle porosity and
irregularly shaped vugs make up the 5% porosity found in the sample.
In thin section, the sandy peloidal wackestone is composed of 40 %
quartz grains and 10 % peloids.
The quartz grains are subrounded to
rounded, very well sorted, and average 0.008 mm in diameter. The
matrix has been dolomitized with the crystals medium to coarse in
size. The quartz grains all exhibit undulatory extinction.
The
peloids, probably pellets, average 0.008 mm in diameter and are evenly
distributed throughout the sample. The pellets are ovoid, though some
are squashed and appear to have been completely micritized. There are
larger peloids composed of several pellets squashed together.
Porosity is <5% and is in the form of void spaces within the matrix.
54
The other rock type in the lower Oxyoke Canyon Sandstone is a
quartzite. In thin section, approximately 30 % of the grains were
found to be in optical continuity. The grains range from 0.25 to 0.5
mm in diameter. The grain boundaries are planar with some enfacial
triple junctions. Several of the grains were observed to have quartz
overgrowths.
A few fractures have been infilled with chalcedony.
Oxyoke Canyon Sandstone, upper member
The upper unit of the Oxyoke Canyon Sandstone is a dolomitic
mudstone.
The upper unit is best exposed in the Mulligan Gap area;
overall, the southern exposures are the most extensive. In the
central map area, the upper unit is medium gray on fresh surfaces and
light gray where weathered. The dolomite is moderately well-bedded
with bedding plane partings approximately one foot apart. In the
southern portion of the mapping area the dolomite is brownish gray on
fresh surfaces; weathered surfaces are a light brownish gray. The
dolomite in the central portion is highly fractured, and in the south
the dolomite tends to be.brecciated and fetid. Both the central and
southern exposures have quartz-rich dolomite at the base; this
dolomite decreases in quartz content upsection. The quartz-rich base
55
is a transitional unit between the sandy peloidal wackesbone-packstone
of the lower member and the dolomite of the upper member. The
transitional unit is finely laminated, with quartzose layers
interbedded with dolomitic mudstone. The quartzose layers are
undulatory with some small-scale scour-and-fill structures.
In thin section, the transitional unit is seen to be a
dolomitized mudstone with undulatory sandy interbeds which range from
2 to 4 mm thick. The quartz grains are very fine- to fine-grained,
some are in grain-to-grain contact, and some are in matrix support.
The mudstone is very finely laminated. The laminations and the
quartzcse interbeds have been disturbed by burrowing organisms.
Although the burrows are randomly oriented, most are vertical. The
downward displacement of the quartz grains into the mud layers is the
most obvious evidence of burrowing. Porosity is <5% and is in the
form of fractures. Some of the fractures have produced small-scale
normal "faults". These small-scale "faults" resulted in the formation
of small-scale grabens of quartzose interbeds.
The thin sections of the upper Oxyoke Canyon Sandstone studied
were found to be a dolomitic mudstone and a sandy crinoidal dolomite.
The dolomitic mudstone is composed of a mosaic of finely crystalline
56
dolomite.
Crystal boundaries are irregular and the dolomite is
cloudy. Approximately 1% angular very fine-grained quartz is present.
Irregularly shaped vugs and fractures make up the estimated 10 %
porosity in the rock. The infilling matprial is dolomite, calcite,
and chalcedony.
The sandy crinoiaal dolomite is composed of 20%
quartz grains and 20 % fossil materiAl, All the grains are in matrix
support. The quartz grains are angular to subrounded and very fine in
size. Some of the grains have coalesced and now display enfacial
triple junctions. The crinoid columnals are extremely leached, making
identification difficult. The dolomite crystals range from finely to
coarsely crystalline, the average size being about 0.8 mm in diameter
or coarsely crystalline. In addition, 10% of the rock is estimated to
be pore space. The porosity is in the form of vugs partially filled
with dolomite and fractures partially filled with chalcedony.
57
SENTLNEL MOUNTAIN DOLOMITE
General Statement
The Sentinel Mountain Dolomite was originally described as part
of a five-fold subdivision of the Nevada Formation by Nolan et al.
(1956).
They described the Sentinel Mountain as being entirely
composed of alternating beds of light and dark dolomite. In
1957,
Carlisle et al., in their subdivision of the Nevada Formation in the
Sulphur Spring and Pinyon Ranges, described a sequence of alternating
beds of light and dark dolomite which they called the Telegraph Canyon
Member.
Both the Telegraph Canyon and Sentinel Mountain are Middle
Devonian. Hose et al.
formational status.
(1982)
raised the Sentinel Mountain Dolomite to
Kendall et al.
(1983)
noted that the lower unit
of the Telegraph Canyon Member is correlative with the Sentinel
Mountain Dolomite. Johnson and Murphy
(1984)
proposed a revision of
the stratigraphic nomenclature in which they suggested a rejection of
duplicate names. The lower unit of the Telegraph Canyon was dropped
in favor of the Sentinel Mountain Dolomite as a matter of simple
priority.
The Sentinel Mountain Dolomite, like the Oxyoke Canyon
58
Sandstone, is an alloctthonous unit, brought into the area as a result
of low-angle normal faulting.
Litho logy And Outcrop Characteristics
In the map area, the Sentinel Mountain occurs as an alternating
brownish gray to medium gray, mottled dolomite.
The brownish gray dolomite
are light brownish gray to light gray.
tends to be fetid.
The fresh surfaces
The unit forms one to six foot thick benches with
the benches spaced 10 to 50 feet apart.
In the field, the Sentinel
Mountain closely resembles the Old Whalen because of similar color and
outcrop pattern.
The Sentinel Mountain does not contain the gray
dolomite of the Old Whalen, however.
The lithology of the formation
varies from a sandy dolomite at the base to a dolomitic cdrwlicial
wackestone and finally to a dolomitic mudstone.
The bed is exposed at only two
unit there is a localized breccia bed.
locations (near JL-54, see Plate 1).
At the base of the
The breccia consists of angular
clasts, from <1 inch to 2 inches across, composed of dolomitized sandy
pekAdal wackestone in martiix support.
iron-stained.
The matrix is heavily
59
The Sentinel Mountain Dolomite in thin section is seen to be a
very finely to finely crystalline laminated dolomite. The laminations
are <0.25 mm thick. The formation contains only 1% very fine quartz
grains, which are extensively leached.
One sample contains
approximately 5% unident-ifiahlp fine-sized fossil fragments.
The
long axes of the fossils have a subparallel alignment. The dolomite
crystals have a mcsaic texture with fairly straight boundaries. The
crystals are cloudy, probably a result of the finely disseminated
organic matter. The dolomite contains vertical burrows which disturb
the very fine laminations. Because of the homogeneity of the rock,
the dolomite was probably a mudstone. The fractures and vugs in the
rock have been infilled with dolomite.
The breccia unit found near the base of the Sentinel Mountain
Dolomite is seen in thin section to be a dalomitized sandy peloidal
wackestone breccia. The clasts are subrounded to rounded, and range
from 0.008 to 2 mm in diameter.
The larger clasts do not contain any
peloids; but are a dalomitized sandy wackestone. The dolomite is very
fine to medium crystalline. The matrix is extensively leached and
iron-stained. The clasts also contain irregular blebs of chalcedony.
60
Contacts And Age
The Sentinel Mountain Dolomite is part of the allochthonous
package which includes the Sadler Ranch, Oxyoke Canyon Formation, and
the Garden Valley Formation.
The Sentinel Mountain overlies the
Oxyoke Canyon Sandstone with what appears to be a concordant contact.
That contact, however, is a low-angle normal fault, with the breccia
bed at the base of the Sentinel Mountain possibly marking the trace of
the fault that separates the two units.
The Sentinel Mountain was dated utilizing conodonts. A sample
(JL-54) was obtained approximately 50 stratigraphic feet above the
be of the unit. The conodonts found in the dolomite range from the
australis Zone to the Lower varcus Subzone (Mapper, written
communication, 1985).
Middle Devonian.
This places the Sentinel Mountain within the
61
GARDEN VALLEY FORMATION
The Permian Garden Valley Formation forms a prominent ridge along
the western margin of the map area. The Garden Valley Formation was
first described by Nolan et al. (1956). The type locality is located
approximately two miles south of the study area. At the type locality
Nolan et al. (1956) described four members for the Garden Valley.
The
member which is found in the map area is the reddish brown silicified
conglomerate member (see Figure 13). At the type locality the
conglomerate is 900 to 1000 feet thick and overlies another silicified
conglomerate.
The reddish brown conglomerate is composed of angular
to subrounded, coarse sand to cobble-sized clasts, which are clastand matrix-supported.
The clasts are multi-colored and are composed
of microcrystalline quartz. The rock has been thoroughly silicified;
in some samples the clasts are merely dark blebs in the matrix. At
some outcrops, the conglomerate is darker in color, almost black.
Most is reddish brown, which gives the ridge along the western margin
of the map area a red color. The eroded material from the formation
also has a distinctive red color. The contact between the Garden
Valley Formation and the other units is a north-south normal fault
which runs the length of the map (see Plate 1). The basal contact of
the formation is a low-angle normal fault (see Plate 2) as the Garden
Valley is the youngest of the allochthonous rocks in the map area.
62
Figure 13.
Hand sample of the reddish brown silicified conglomerate
from the Garden Valley Formation.
63
DEPOSITIONAL HISTORY
Several rock units were deposited from the latest Ordovician to
the Middle Devonian in a shallow sea covering a carbonate shelf at the
present-day site of the southern Sulphur Spring Range.
During the latest Ordovician, the finely crystalline, dolomitic
crinoidal mudstones and wackestones of the Hanson Creek Formation were
deposited in a low-energy lagoon.
The environment of deposition was
determined by Dunham (1977). Dunham studied the Hanson Creek
Formation in several areas in Eureka County, but the most applicahlp
to this study are the Lone Mountain and Pete Hanson Creek sections;
with the latter located in the Roberts Mountains. He concluded that
the Hanson Creek was deposited in four distinct environments. The
high energy shoals, according to Dunham (1977), dissipated the wave
and current energy so that mud-sized material was then deposited in
quiet lagoons shoreward of the shoals. The sections at both Lone
Mountain and Pete Hanson Creek contain wackestone and mudstone with
pelmatazoan columnals.
The Pete Hanson Creek section is dominated by
mudstone with wackestone interbeds. Dunham (1977) also noted that the
fossils present indicate that water circulation must not have been
64
restricted. The fossil content of the Hanson Creek in the southern
Sulphur Spring Range is between 5 and 10%, of which all are crinods.
Their presence could indicate, as Dunham noted, an unrestricted water
circulation, allowing organisms to exist in the lagoon. However, the
crinoids found in the map area are disarticulated and do not appear to
exceed 2 mm in length. In the case of the southern Sulphur Spring
Range these crinoirls were probably washed into the lagoon as the
result of storms. The samples studied from the Hanson Creek are not
laminated and the crinoids are randomly oriented; therefore,
conditions must have been such as to allow burrowing organisms to
exist and stir up the substrate.
A late Llandoverian hiatus has been documented by Murphy et al.
(1979) between the Hanson Creek and the Roberts Mountains Formation.
Johnson and Murphy (1984) have projected this unconformity beneath the
Lone Mountain Dolomite.
Because the Lone Mountain Dolomite is a secondary dolomite,
interpretation of the depositional environment is not possible from
field or thin section study. However, several authors (Winterer and
Murphy, 1960; Math and McKee, 1977; Johnson and Sandberg, 1977;
Mullen, 1980) have concluded that the Lone Mountain Dolomite forms a
couplet with the Roberts Mountains Formation. The Roberts Mountain
65
Formation is the deeper-water equivalent of the Lone Mountain. Rocks
of the Roberts Mountains Formation are basinal limestones and reef
flank deposits.
The Lone Mountain Dolomite is a reef complex from
which the reef flank deposits of the Roberts Mountains were derived.
The time of deposition of the couplet was from the late Llandoverian
to the Lochkovian (Johnson and Murphy, 1984).
A hiatus occurred from the Pridolian to the early Lochkovian
(Johnson and Murphy, 1984), after which the upper member, the Old
Whalen, of the Lone Mountain Dolomite was deposited during the late
Lochkovian (Klapper and Murphy, 1980).
The Old Whalen Member represents a variety of repeating rock
types, as noted by Colman (1979), that indicates different recurring
shallow marine environments on a broad carbonate platform. The brown
fetid dolomite represents rapid burial or burial in an oxygen-poor
environment, with consequent preservation of the organic matprial,
The gray non-fetid dolomite indicates either slower deposition or
deposition in oxygenated water where organic matter was destroyed.
The presence of peloids in the brown fetid dolomite also indicates
anoxic conditions; the few fenestrae present indicate rapid burial,
The brown dolomites of the Old Whalen were deposited in areas of quiet
water, which were slighty restricted in circulation. The dark color
66
and the fact that the dolomite is fetid would indicate either rapid
deposition or deposition under anoxic conditions.
However, the
presence of pelaids and skeletal material indicate that conditions
were probably not anoxic. The lack of abundant fenestrae indicate
rapid deposition. Fossils above the substrate, within the dolomite
are whale or fragmented rugose corals and crinoids. The presence of
crinoirls indicates open marine conditions. The fine crystallinity of
the dolomite and the fragmented nature of some of the fossils also
implies that the fossils were broken up on a high energy shoal and
then washed into a shoreward basin or lagoon. The corals, which are
found whole, could have lived along the margins of the basin because
the rugose variety can exist on soft substrates.
The gray dolomites represent a change in the site of deposition,
as they are not fetid. The dolomite, where laminated, is only poorly
laminated and contains peloids as well as fragments of gastropods and
trilobites. The gray dolomite must have been deposited more slowly
than the brown dolomite because the overall massive character of the
gray dolomite would indicate bioturbation. Also, the slower rate of
deposition may have led to the accumulation of trilobite and gastropod
fragments in the gray dolomite versus rugose coral and crinoirls in the
brown dolomite. However, the amount of fossil material is more
important; in the brown skeletal fragment dolomite up to 50 % of the
67
total rock is allochems, of which 30 % is fossil material. In the gray
peloidal dolomite 20% of the total rock is allochems of which <5% is
fossil material. The overall lower volume of allochems, especially
fossil material, suggests that the amount of material coming from the
high-energy shoals was probably less in the gray dolomite.
The gray dolomite may represent a period of low-energy
deposition; whereas the brown dolomite represents a higher energy
deposition on the shoals, which would lead to a greater volume of
material coming into the basin during a given period of time. The
flood of material causing rapid burial, prevented the substrate from
being bioturbated. The cause of the episodic "flooding" of material
may have been the result of storms.
A major unconformity is present between the Old Whalen Member and
the base of the K obeh Member. This unconformity marks the end of the
Tippecanoe sequence and the base of the K obeh Member represents the
begining of the Kaskaskia sequence (Sloss, 1963; Johnson and Murphy,
1984).
68
Deposition of the Kobeh Member began in the e.arly Pragian. The
Kobeh Member was deposited on a shallow shelf under normal marine
conditions. The abundant shelly fauna indicates shallow water depths;
the crinoids indicate open circulation. Organic activity remained
high during deposition as manifested by the presence of peloids
throughout the unit.
Fossils in the packstones display a subparallel
orientation whereas those in the wackestone are randomly oriented.
The packstone was deposited or possibly re-worked during storms as
evidenced by the subparallel alignment of the fossil fragments and the
lack of mud. The wackestones were deposited and then bioturbated as
indicated by the lack of laminae and by the random orientation of the
fossils.
However, bioturbation was not pervasive, as is indicated by
the presence of mud interbeds in one peloidal wackestone sample.
The
sand found throughout the Kobeh could be either ealian or fluvial by
transport across the Sevy-Beacon Peak tidal flats. Kendall (1975,
Fig. 4) plotted the distribution of a basal quartzite of the
Sevy-Beacon Peak Dolomite.
The source of the quartzite was to the
north and east of the map area, or shoreward of the Kobeh outcrops in
the Sulphur Spring Range. Because this sand is present throughout the
Kobeh it was probably carried out to the shelf by currents. The
currents sorted the sand so that only the finest fraction was
deposited off shore.
69
Directly following deposition of the Kobeh was the deposition of
the Bartine Member of the Mc Colley Canyon Formation. The initial
deposits of the Bartine were laid down in the latest Pragian-earliest
Emsian.
The Bartine was also deposited in a shallow shelf, normal
marine environment, and like the Kcbeh, was affected by variable
However, the Bartine appears to be a deeper deposit than
currents.
the Kcbeh.
The Bartine contains more mud than the Kobeh and the fossils in
the wackestones are whole or disarticulated, not fragmented as in the
Kobeh.
The effect of the variable currents or storms caused the
fomils in the packstones to be nested, with the brachiopods and
trilobites oriented concave down. Additional evidence for the Bartine
being farther offshore than the Kobeh is the presence of thin mudstone
beds found in between the fossil layers in the packstones. The mud
remained because of the diminished effect of currents in the deeper
water. The inverse relationship between fossil material and quartz
grain content in the packstone is probably storm-related. The
stronger currents could have caused both the sand and fossil material
to be swept farther out into the basin than usual, but with the fossil
material being carried farther offshore than the sand. The peloids
and abundant shelly fauna which are found throughout the unit indicate
that organic activity was high. Burrows observed in the thin sections
indicate that the bottom was not anoxic and that deposition was not
70
sufficiently rapid to prevent bioturbation. The upper part of the
Bartine represents further deepening of the basin during the late
Emsian.
The medium gray color of the upper Bartine versus the
yellowish gray of the lower Bartine indicates a deeper water
deposition for the upper.
Quartz grains compose 1% of the total rock,
although in the lower unit, they compose up to 30%. Bedding is better
developed in the upper Bartine, and there appears to be no evidence of
bioturbation. The lack of shelly fauna would also indicate deeper
water than in the lower Bartine. The variable currents were still
effective, however, as evidenced by the parallel orientation of the
crinoid bedding.
The presence of lithoclasts in the packstone
indicates that reworking of the substrate occurred. This could have
been the result of downslope movement of the substrate or from
storm-induced currents reworking the substrate.
Crinoids, being the
principal fossil, indicate an open marine circulation.
The Sadler Ranch Formation was deposited during the late Early
Devonian.
The dolomitic crinoid, and crinoid-brachiopod wackestones
were deposited on a shallow shelf under normal marine conditions. The
Shelly fauna indicate shallow water depths and the crinoids indicate
open circulation. However, conditions were not stable; as is
71
indicated by the thin mudstone bed and the packstone.
The mudstone
bed, within the wackestone, suggests an interval of lower depositional
energy.
The packstone is the result of increased depositional energy
with the subsequent winnowing of any mivis that were present. The
packstone was probably deposited during or reworked by a storm. The
overall. ma give bedding, except in the mudstone bed, indicates
bioturbation took place throughout deposition. The very fine grains
of quartz found in the Sadler Ranch were probably derived from the
beach-bar-dune deposits found in the Oxyoke Canyon Sandstone.
The Oxyoke Canyon Sandstone is the shoreward correlative of the Sadler
Ranch Formation.
The lower member of the Oxyoke Canyon Sandstone was
probably deposited in a high to moderate energy lagoon.
The lag000n
had open circulation as indicated by abundant peloids found throughout
the unit. The dolomite matrix indicates a shallow water environment.
The pPlnirls show that organic activity was high. The high to moderate
depositional energy is indicated by lack of mud, as in the peloidal
packstone, and by the croa-laminae in the middle of the unit. The
decrease in depositional energy in the lagoon resulted in the
deposition of the dolomitic mudstone of the upper member of the Oxyoke
Canyon Sandstone.
The decrease in energy is suggested by the
dolomitic mudstone with quartz interbeds which become dominantly
dolomitic mudstone upsection. However, the lagoon retained an opening
72
to the sea as is indicated by the presence of acinoirls. Bioturbation
continued throughout deposition; as is documented by the downward
displacement of some of the quartz interbeds, and in the overall
massive character of the mudstone.
The Sentinel Mountain Dolomite was deposited in an environment
that was similar to that of the upper member of the Oxyoke Canyon
Sandstone; probably in a lagoon that initially had open circulation
and that was later, at least partially, isolated from the sea. The
sandy dolomite and the dolomitic ctinoidal wackestone were deposited
during the time of open circulation. The dolomitic mudstone was
deposited during a time of restricted circulation, but not
sufficiently restricted as to limit organic activity. The mudstone is
dark in color and fetid, but shows evidence of bioturbation.
73
STRUCTURE
The prominent structural features in the southern Sulphur Spring
Range are a Cretaceous? age low-angle normal (denudation) fault and
the steeper more typical normal faults of Tertiary age. The
all.ochthonous post-Bartine 6 ata were emplaced by the Cretaceous?
low-angle normal fault. The Tertiary normal faults resulted in
typical Basin and Range fault-block topography of the area.
Cretaceous? Low-angle Normal Faults
The low-angle normal faults were discovered by studying the
stratigraphic succession, with the aid of paleontological age
determinations obtained from the conodonts. The conodonts identified
the units more precisely than lithology because of overall lithalogic
similarities of some of the units, i.e. the Sentinel Mountain Dolomite
and the Old Whalen. The stratigraphic succession was found to vary
throughout the map area, with the variance always occurring above the
Kobeh Member.
The overlying Bartine Member appears to be cut out in
74
places by the lower unit of the Oxyoke Canyon Sandstone (see Figure
14), especially north of the Mulligan Gap area.
The stratigraphic succession with low-angle normal faults is
illustrated in Figure 14. Stratigraphic relationships between the
various rock units would be difficult to explain without the low-angle
normal faults.
The Bartine Member is incompletely cut out by the
shallow water high-energy lower Oxyoke Canyon Sandstone. However,
the Bartine has not been removed in the southern map area (JL-123).
The present day juxtaposition of the formations (see Figure 14) shows
the lower Oxyoke overlying on an almost complete sequence of Bartine,
i.e. both the upper and lower parts of the Bartine Member are present.
In the central portion of the map area, the Bartine is completely
missing, with the Oxyoke Canyon rocks overlying the Kobeh Member. As
shown in plate 2 (section A-A'), the lower Oxyoke in the east, is
found on the Old Whalen with both the Bartine and Kobeh removed, but
not by erosion. Also, in the eastern portion of the map, the Sentinel
Mountain Dolomite lies directly on the lower Oxyoke Canyon, whereas
the upper Oxyoke is not present. The fades diagram given by Figure
15, shows the lower Oxyoke Canyon as pinching out; the dolomites of
the upper Oxyoke Canyon lie on top of the sandstones and pelok1al
packstones of the lower Oxyoke.
o
0-..t.
South
North
Low-angle normal fault --MWM--AMn
nippy
JL-123
1
,----
Doxu
-1-,
0
0
,
cl-1
1
4-1
M
M
rr
Doxl
Dmb
0
.1-1
El
Dmk
o
,---"""--",-/1,----",/"W-...-----,...-----,----Nz------,.....-
__,".,/--s./''
.
1
Dirnow
Figure 14. Present juxtaposition of formations in the southern Sulphur Spring Range.
Facie::
Plnco
Lone Mountain
Southern Sulphur spring Range
1
Source,
Kendall
et ni., 1903
I
2
Sulphur
Kendall et al.,
1983
Sentinel Mtn.
Dolomite
Sentinel Mtn.
Dolomtte
In the Southern Sulphur
Spring Range, otratigraphic
sections 1, 2, and 3, are
locatod near the following
fosuil locolitleo (see
Plate 1):
Diamond Range
Spring Ron.g2
3
Thin Paper
Denny
Limontono
1
I
EXPLANATION
Transitional & Lau tern
TrannitIonal
Wel:tern
Belt
Nolan et al.
1956
Sentinel
Mm.
2
Mbr.
0
11111-111111-1110L-
t-
I
w
upper
Member
m
vi
11
Black rectangles denote
horizono affected by
low-angle normal faulting.
Oxyoke Canyon
Po/Illation
If
Z1
Oxyoke
Canyon
Sadler Ranch
Formation
Mbr.
Oxyokc Canyon Sandstone
lower member
-1211-11111-11:21-1Cla
_ONLABIL
Sadler
Ranch
Fm.
Sadler
Rancl Fm.
moo is jra
o
111
rrt
uppe
Coils Creek
Bartine Tongue
Mbr.
..4
,
]
3
JL-119
JL-54
JL-123
g
p
w
3.
o
14
14
o
...
Datine
Mbr.
Bartino
Beacon Peak
U. Tongue
Mbr.
Bartino
lower part
Koboh
Koboh
Kobeh
Kobel:
Mbr.
Mbr.
Mbr.
Mbr.
w
H
H
00
Lone Mtn.
Dolomite
Figure15.
Old Ullle Member
Beacon
Peak
br.
Bartino
Mbr.
Mr.
>,.
Deacon
Peak
Dolomite
Lone Mountain Dolomite
Correlation chart for part of the Lower and Middle
Devonian.
77
As shown in the correlation chart (see Figure 15), the
stratigraphy in the southern Sulphur Spring Range is not totally
compatible with that in other areas of the county.
Kendall (1975) has
demonstrated that the Sadler Ranch Formation overlies the Bartine
Tongue in the central and northern portions of the Sulphur Spring
Range.
The Sadler Ranch is, in turn, directly overlain by the Oxyoke
Canyon Formation. To the south of the Sulphur Spring Range, at Lone
Mountain, the Sadler Ranch Formation is underlain by the Coils Creek
Member of the Mc Colley Canyon Formation, and is overlain by the Denay
Limestone.
East of the Sulphur Spring Range, in the Diamond Range,
the Oxyoke Canyon is underlain by the Beacon Peak, and is overlain by
the Sentinel Mountain Dolomite.
Elsewhere there are units missing
from the normal stratigraphic succession in the southern Sulphur
Spring Range (see Figure 15); i.e. the Oxyoke Canyon Sandstone lies
directly on Bartine Member with no Sadler Ranch present, and the
Sentinel Mountain Dolomite overlies the lower member of the Oxyoke
Canyon with the upper portion of the Oxyoke Canyon missing (location
2, Figure 15). Also at location 2, the Sadler Ranch Formation lies
directly upon the Old Whalen Member with the Mc Colley Canyon rocks
missing
The Sadler Ranch Formation, Oxyoke Canyon Formation, and Sentinel
Mountain Dolomite display a complicated relationship with other rock
78
units in the area. Explanation for these relationships using fades
changes would require anomalous changes in the depositional
environment, that would not be in agreement with W alther's laws of
fades. The simplest solution to these stratigraphic problems is
obtained from structural investigations. Low-angle normal faults are
commonly characterized by the juxtaposition of younger strata over
older, with the removal of strata, or denudation, at horizons affected
by the faults. The southern Sulphur Spring Range is a prime example
of this phenomenon. The Lower to Middle Devonian Oxyoke Canyon
Sandstone, along with the Sadler Ranch Formation and the Sentinel
Mountain Dolomite, have been juxtaposed on the Lower Devonian Old
Whalen, Kobeh, and Bartine Members. The incomplete removal of the
Bartine Member and the complete removal of the post-Bartine units also
took place (see Figures 14 and 15).
The solution to the succession problem is believed to be in the
low-angle normal faults.
Low-angle normal or denudation faults have
been studied in eastern Nevada by Armstrong (1972) and other workers
(Coney, 1974; Hose and Blake, 1976). Low-angle faults are the product
of extension, and, in the case of the southern Sulphur Spring Range,
were probably related to the Cretaceous Sevier orogeny. There has
been disagreement among the various investigators as to the timing of
the low-angle faulting. For example, was the movement a Cretaceous or
a Tertiary event? The answer cannot be found in the southern Sulphur
Spring Range because of the lack of any cross-cutting dikes or other
79
age-determinable units.
A Cretaceous age of movement on the
low-angle fault in the southern Sulphur Spring Range is presumed
because of the eastern source and the pre-Cretaceous age of the
allochthonous rocks.
The age is still problematical as a consequence
of the lack of evidence for the time of movement. Johnson (1986,
written corn mmunication) has stated that the source of the
allochthonous rocks was to the east because there is not an example in
estahlished stratigraphy of Oxyoke Canyon over a full develpoment of
Bartine, as is juxtaposed in the southern Sulphur Spring Range.
The
Oxyoke Canyon Sandstone and the remainder of the allochtonous package,
therefore, must have come from the east.
As indicated on the A-A' cross- section in Plate 2, the Garden
Valley Formation is also part of the allochthonous package.
This is
in agreement with drill data (J. P. Graham, 1986, written
communication) showing that four wells drilled in Diamond Valley ( T
23N-R 54E-NE NW 30, T 24N-R 53E-NW NW 24, T 21N-R 53E-NE NW 1, and T
21N-R 53E-NE NE 11.) go directly from valley fill into rocks of
Devonian age without the 'presence of the Garden Valley Formation above
the Devonian. However, the presence of the Permian Garden Valley
Formation to the west constitutes additional evidence of an eastern
source in that the Garden Valley Formation would have to be absent if
the source was immediately to the west.
80
The eastern source is inferred to have been located at the
present-day site of Diamond Valley.
The allochthonous package was
probably transported less than 10 miles to its present position. This
relatively short distance of transport might also explain the
inclusion of the Sadler Ranch Formation in the allochthonous package.
The Sadler Ranch is present to the north of the map area and was
probably present to the east. The allochthonous rocks were later
again displaced by the Tertiary normal faults.
Tertiary Normal Faults
Normal faults of Tertiary age have served to control the
present-day topography of the area. Moreover, the present-day
attitude of the low-angle fault plane and the distribution of the
allochthonous blocks are also related to the Tertiary faulting. This
structural event caused the dismemberment of the K obeh and Old Whalen
units and exposed the Hanson Creek and Lone Mountain Dolomite units in
the south (see Plate 2, section B-13').
81
CONCLUSIONS
The Ordovician through Middle Devonian rocks mapped in the
southern Sulphur Spting,,range were deposited as shallow water
sediments in a westward thickening wedge, the Cordilleran geosyncline.
This pattern of sedimentation changed with the Late Devonian Antler
orogeny.
The Hanson Creek Formation was probably deposited in a lagoon
during the latest Ordovician.
Overlying the Hanson Creek Formation,
with a gradational contact, is the lower member of the Lone Mountain
Dolomite.
The lower member of the Lone Mountain Dolomite is a
secondary dolomite that has been interpreted to be a reef complex.
The Old Whalen Member of the Lone Mountain Dolomite is the unit with
the greatist areal extent in the map area. The Lower Devonian Old
Whalen Member represents a repetition of recurring shallow marine
environments on a broad carbonate platform. Overlying the Old Whalen
Member is the Kobeh Member of the McCalley Canyon Formation.
Deposition occured on a shallow shelf under normal marine conditions
during the early Pragian. Overlying the Kobeh Member is the
abundantly fossiliferous lower part of the Bartine Member of the
82
Mc Calley Canyon Formation.
The initial deposits of the lower part of
the Bartine were laid down in the latest Pragian-earliest Emsian on a
shallow shelf under normal marine conditions, but in deeper water than
the Kcbeh Member. The upper part of the Kobeh, found as a single
outcrop, is sparsely to moderately fossiliferous. The upper part of
the Bartine Member was deposited in the late Emsian and in deeper
water than was the lower part.
The Sadler Ranch Formation is the first of the allochthonous
units found in the map area. The oinoirlal dolomites of the Sad er
Ranch Formation were deposited in the late Early Devonian on a shallow
shelf in shallow water with open circulation.
The second
allochthonous unit mapped is the Oxyoke Canyon Sandstone. The
peloidal limestones, and quartzites of the lower member of the Oxyoke
Canyon Sandstone were deposited in a high to moderate energy lagoon.
A change in the depositional energy in the lagoon resulted in the
deposition of the dolomitic mudstones of the upper member of the
Oxyoke Canyon Sandstones.
The Sentinel Mountain Dolomite is the third
allochthonous unit found in the study area. The Middle Devonian
Sentinel Mountain Dolomite was deposited in a lagoon that initially
had open circulation which was later, at least partially, cut off.
83
The Permian Garden Valley Formation is the fourth allochthonous unit
found in the map area. The silicified conglomerates of the Garden
Valley Formation were deposited as a result of the highland developed
during the Antler Orogeny shedding sediments into an adjacent foreland
basin.
The significance of the Sadler Ranch Formation, Oxyoke Canyon
Sandstone, and Sentinel Mountain Dolomite is their stratigraphic
position, i.e. the juxtaposition of these units over the Lower
Devonian units.
The complex stratigraphy of the post-Bartine units
led to the discovery of low-angle normal faults, which juxtaposed the
Sarller Ranch Formation, Oxyoke Canyon Sandstone, and Sentinel mountain
Dolomite rocks over the Old Whalen Member and M c C alley Canyon
Formation.
The low-angle normal faults also caused the partial to
complete denudation of the Kobeh and Bartine Members, and the
emplacment of the Permian Garden Valley Formation rocks along the west
side of the map area.
The key factor in verifying the lithologic evidence was the ages
obtained for the various rock units, utilizing conodonts.
The dates
obtained from the conodonts placed the units within known time frames
from which the stratigraphy was worked out. The stratigraphic
succession was vital to the discovery of the low-angle normal faults.
84
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GeoL Soc. America Bull., v. 79, p. 427-458.
, 1972, Low-angle (denudation) faults, hinterland of the
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Soc. America Bull., v. 83, p. 1729-1754.
Carlisle, Donald, Murphy, M. A., Nelson, C. A., and Winterer, E. L.,
1957, Devonian stratigrphy of Sulphur Spring and Pinyon Ranges,
Nevada: Am. Assoc. Petroleum Geologists Bull., v. 41,
p. 2175-2191.
Colman, R. L., 1979, The carbonate petrology and conodont
biostratigtaphy of the Old Whalen Member of the Lone
Mountain Dolomite (Lower Devonian), Sulphur Spring Range,
Nevada: unpublished M. S. thesis, University of California,
Riverside, California, 116 p.
Coney, P. J., 1974, Sructural analysis of the Snake Range
decollernent, east-central Nevada: GeoL Soc. America BulL,
v. 85, p. 973-978.
Dunham, J. B., 1977, Depositional environments and paleogeography of
the Upper Ordovician, Lower Silurian carbonate platform of
central Nevada, in Stewart, J. H., Stevens, C. H., and
Fritsche, A. E., eds., Paleozoic paleogeography of the western
United States: Soc. Econ. Paleontologists and Mineralogists,
Pacific Section, Pacific Coast Paleogeography Symposium 1, p.
157-164.
Dunham, R. J., 1962, Classification of carbonate rocks according to
depositional texture, in Classification of carbonate rocks, a
symposium: Am. Assoc. Petroleum Geologists Mem. 1, p. 108-121.
Folk, R. L., 1965, Some aspects of reczystallization in ancient
limestones, in Dolomitization and limestone diagenesis-A
symposium: Soc. Econ. Paleontologists and Mineralogists Spec.
Pub. 13, p. 14-48.
85
Gronberg, E. C., 1967, Stratigraphy of the Nevada Group at Lone
Mountain and Tal-ilp Mountain, central Nevada: unpublished M. S.
thesis, Unversity of California, Riverside, California, 83 p.
Hague, Arnold, 1892, Geology of the Eureka district, Nevada:
U. S. GeoL Survey Mon. 20. 419 p.
Hose, R. K., and Blake, M. C., 1976, Geology, Pt. I, in Geology and
mineral resources of White Pine County, Nevada: Nevada Bur.
Mines and Geology BulL 85, p. 1-32.
Hose, R. K., Armstrong, A. K., Harris, A. G., and Mamet, B. L., 1982,
Devonian and Mimissippian rocks of the northern Antelope Range,
Eureka County, Nevada: U. S. Geol Survey Professional Paper
1182, 19 p.
Johnson, J. G., 1962, Lower Devonian-Middle Devonian boundary in
central Nevada: Am. Assoc. Petroleum Geologists BulL, v. 46.,
p. 542-546.
, 1977, Lower and Middle Devonian faunal intervals in
central Nevada based on brachiopods, in Murphy, M. A., Berry,
W. B. N., and Sandberg, C. A., eds., Western North America
Devonian: University of California, Riverside, Campus Museum
Contributions 4, p. 16-32.
Johnson, J. G., and Murphy, M. A., 1984, Time-rock model for
Siluro-Devonian continental shelf, western United States:
Geol. Soc. America BulL, v. 95, p. 1349-1359.
Johnson, J. G., and Sandberg, C. A., 1977, Lower and Middle Devonian
continental-shelf rocks of the western United States, in
Murphy, M. A., Berry, W. B. N., and Sandberg, C. A., eds.,
Western North America Devonian: University of California,
Riverside, Campus Museum Contributions 4, p. 121-143.
86
Kendall, G. W., 1975, Some aspects of Lower and Middle Devonian
stratigraphy in Eureka County, Nevada: unpublished M. S. thesis,
Oregon State University, Corvallis, Oregon, 199 p.
Kendall, G. W., Johnson, J. G., Brown, J. 0., and Klapper, Gilbert,
1983, Stratigraphy and fades acmes Lower Devonian-Middle
Devonian boundary, central Nevada: Am. Assoc. Petroleum
Geologists Bull., v. 67, p. 2199-2207.
Klapper, Gilbert, 1977, Lower and Middle Devonian conodont sequence in
central Nevada, with contributions by D. B. Johnson, in
Murphy, M. A., Berry, W. B. N., and Sandberg, C. A., eds.,
Western North America Devonian: University of California,
Riverside, Campus Museum Contributions, p. 33-54
Mapper, Gilbert, and Murphy, M. A., 1980, Conodont zonal species from
the delta and pesavis Zones (Lower Devonian) in central
Nevada: Neues Jahrbuch fur Geologie and Palaontologie
Monatsheft, v. 8, p. 490-504.
Math, J. C., and McKee, E. H., 1977, Saurian and Lower Devonian
paleogeography of the outer continental shelf of the Cordilleran
miogeodine, central Nevada, in Stewart, J. H., Stevens, C.
H., and Fritsche, A. E., eds., Paleozoic paleogeography of the
western United States: Soc. Econ. Paleontologists and
Mineralogists, Pacific Section, Pacific Coast Paleogeography
Symposium 1, p. 181-215.
Merriam, C. W., 1940, Devonian stratigraphy and paleontology of the
Roberts Mountains region, Nevada: GeoL Soc. America Spec. Paper
25, 114 p.
Mullen, T. E., 1980, Stratigraphy, petrology, and some fossil data of
the Roberts Mountains Formation, north-central Nevada: U. S.
GeoL Survey Professional Paper 1063, 67 p.
87
Murphy, M. A., and Gronberg, E. C., 1970, Stratigraphy and correlation
of the lower Nevada Group (Devonian) north and west of Eureka,
Nevada: GeoL Soc. America BulL, v. 81, p. 127-136.
Murphy, M. A., Dunham, John, Berry, W. B. N., and Matti, J. C., 1979,
Late Llandovery unconformity in central Nevada: Brigham Young
University Geology Studies, v. 26, pt.1, p. 21-36.
Nichols, K. M., and Saber ling, N. J., 1977, Depositional and tectonic
significance of Silurian and Lower Devonian dolomites, Roberts
Mountains and vicinity, east-central Nevada, in Stewart, J.H.,
Stevens, C. H., and Fritsche, A. E., eds., Paleozoic
paleogeography of the western United States: Soc. Econ.
Paleontologists and Mineralogists, Pacific Section, Pacific
Coast Paleogeography Symposium 1, p. 217-240.
Nolan, T. B., Merriam, C. W., and Willliams, J. S., 1956, The
stratigraphic section in the vicinity of Eureka, Nevada: U. S.
Geological Survey Professional Paper 276, 77 p.
Roberts, R. J., 1972, Evolution of the Cordilleran fold belt: Geol.
Soc. America BulL, v. 83, p. 1989-2004.
Roberts, R. J., Montgomery, K. M., and Lehner, R. E., 1967, Geology
and mineral resources of Eureka County, Nevada: Nevada Bureau
Mines BulL 64, 152 p.
Sloss, L. L., 1963, Sequences in the cratonic interior of North
America: GeoL Soc. America BulL, v. 74, p. 93-113.
Stewart, J. H., 1980, Geology of Nevada: Nevada Bureau of Mines and
Geology Spec. Pub. 4, 135 p.
Winterer, E. L., and Murphy, M. A., 1960, Silurian reef complex and
associated facies, central Nevada: Jour. Geology, v. 68, p.
117-139.
APPENDIX
88
APPENDIX
FAUNAL LISTS AND LOCALITIES
All localities in Garden Valley 15 minute quadrangle.
Conodont identification and age aRgignments made by Gilbert
Mapper, unit asqignments by J. G. Johnson. Brachiopod
identification, age assignment, and not by J. G. Johnson.
Coral identification by W m. A. Oliver, Jr..
Conodonts
Sample:
Location:
JL-1
E1Pvation 6000 feet, 600 feet north, S. W. corner Sec.12,
T.23 N., R. 52 E..
Pandorinellina expansa
Palygnathus serotinus
Palygnathus linguifonnis bultyncki?
Panderodus sp.
Belodell A sp.
Age:
Unit:
Sample:
Location:
Lower-Middle Devonian, in the range from the serotinus
Zone to the costatus Zone.
Sadler Ranch Formation.
JL-9
Elevation 6040 feet, 1700 feet N., 200 feet S., N. E.
corner Sec.14, T. 23 N., R. 52 E..
Icriodus sp. indet.
Age:
Unit:
Devonian
Oxyoke Canyon Formation.
89
Sample:
Location:
JL-34
Elevation 7120 feet, 6500 feet W., 1500 S., S. W. corner
Sec. 2, T. 23 N., R. 52 E..
Icriodus Clandi a e
Eognathodus sulcatus kindlei
Panderodus sp.
Age:
Unit:
Lower Devonian, kindlei Zone.
Kobeh Member, McColley Canyon Formation.
JL-54
Location: Elevation 6200 feet, 1100 feet E., 300 feet N., S. E.
Sample:
corner Sec. 11, T. 23 N., R. 52 E..
Palygnathus parawebbi
Belodella sp.
Age:
Unit:
Sample:
Location:
Middle Devonian, australis Zone-Lower varcus Subzone.
Sentinel Mountain Dolomite
JL-56
Elevation 6520 feet, 7700 feet W., 700 feet N., S. W.
corner 7ec. 14, T. 23 N., R. 52 E..
Icriodus sp. indet.
Age:
Unit:
Sample:
Location:
Lower Devonian, sulcatus Zone to the serotinus Zone.
Kobeh Member, McColley Canyon Formation
JL-58
Elevation 6800 feet, 8000 feet W., 2100 feet N., S. W.
corner Sec. 14, T. 23 N., R. 52 E..
Icriodus trojani
Polygnathus sp. indet.
Panderodus sp.
Belodell
Age:
Unit:
sp.
Lower Devonian, dehiscens to serotinus Zones.
Bartine Member, McColley Canyon Formation.
90
Sample:
Location:
JL-63
Elpvation 6520 feet, 3200 feet W., 2700 feet N., S. W.
corner Sec. 35, T. 24 N., R. 52 E..
Eognathodus sulcatus kindlei
Icriodus sp. indet.
Age:
Unit:
Sample:
Location:
Lower Devonian, kindlei Zone.
Kobeh Member, McColley Canyon Formation.
JL-65
Elevation 7240 feet, 5600 feet E., 3900 feet N., S. W.
corner Sec. 35, T. 24 N., R. 52 E..
Icriodus claudiae
Pandercdus sp.
Age:
Unit:
Sample:
Location:
Lower Devonian, sulcatus to kindlei Zones.
Kobeh Member, McColley Canyon Formation.
JL-71
Elevation 7040 feet, 6300 feet W., 900 feet S., S. W.
corner Sec. 11, T. 23 N., R. 52 E..
Polygnathus gronbergi
Icriodus sp. indet.
Pandercdus sp.
Age:
Unit:
Sample:
Location:
Lower Devonian, gronbergi Zone.
Bartine Member, Mc Colley Canyon Formation.
JL-74
Elevation 6520 feet., 3000 feet W., 2900 feet S., S. W.
corner Sec. 11, T. 23 N., R. 52 E..
Ozarkodina sp. indet.
Icriodus sp. indet.
Age:
Unit:
Lower Devonian.
Old Whalen Member, Lone Mountain Dolomite.
91
Sample:
JL-89
Location:
R1Pvation 6160 feet, 300 feet E., 1300 feet S., S. W.
corner Sec. 2, T. 23 N., R. 52 E..
Icriodus nevadensis
Icriodus trojani
Pandorinellina sp. indet.
Panderodus sp.
Belodella sp.
Age:
Unit:
Sample:
Location:
Lower Devonian, dehiscens Zone to inverses Zone.
Bartine Member, Mc Colley Canyon Formation.
JL-90
Plgvation 6240 feet, 500 feet W., 2400 feet S., S. W.
corner Sec. 2, T. 23 N., R. 52 E..
Palygnathus n. sp. B
Pandorinellina expansa
Panderodus sp.
Belodella sp.
Age:
Unit:
Sample:
Location:
Lower Devonian, serotinus Zone to patnbis Zone.
Sadler Ranch Formation.
JL-95
P.lpvation 6720 feet, 3200 feet W., 2400 feet S, S. W.
corner Sec. 2, T. 23 N., R. 52 E..
Icriodus claudiae
Age:
Unit:
Sample:
Lower Devonian, sulcatus to kindlei Zones.
Kobeh Member, Mc Colley Canyon Formation.
JL-96
Location: RiPvation 6520 feet, 7000 feet W., 1000 feet N., S. W.
corner Sec. 14, T. 23 N., R. 52 E..
Icriodus claudiae
Age:
Unit:
Lower Devonian, sulc.atus to Icindlei Zones.
Kobeh Member, McColley Canyon Formation
92
Sample:
Location:
JL-116
Elevation 6760 feet, 7300 feet W., 800 feet S., N. W.
corner Sec. 23, T. 23 N., R. 52 E..
Icriodus claudiae
Age:
Unit:
Lower Devonian, sulcatus to kindlei Zones.
Kobeh Member, Mc Colley Canyon Formation.
Sample:
JL-119
Location: Elevation 7000 feet, 5100 feet W., 1500 feet N., S. W. Sec.
26, T. 23 N., R. 52 E..
Polygnathus gronbergi
Pandorinellina exigua exigua
Pandorinellina steinhornensis subsp. inlet.
Icriodus nevadensis
Icriodus trojani
Panderodus sp.
Age:
Unit:
Lower Devonian, gronbergi Zone.
Bartine Member, McColl.ey Canyon Formation.
Sample:
Location:
JL-123
Elevation 7200 feet, 5100 feet W., 1500 feet N., S. W.
corner Sec. 26, T. 23 N., R. 52 E..
Polygnathus laticostatus
Pandatinellina exigua exigua
Icriodus trcrjani.
Icriodus nevadensis
Panderodus sp.
Age:
Unit:
Lower Devonian, inversus Zone.
Upper Bartine Member, McCulley Canyon Formation.
93
Sample:
Location:
JL-129
Elpvation 6080 feet, 2500 feet E., 2400 feet S., S. E.
corner Sec. 35, T. 23 N., R. 52 E..
Amorphognathus ordovicicus
Pseudobelodina dispansa
Drepanaistcdus suberectus
Panderodus sp.
Age:
Ordovician, ordovicicus Zone (Maysvillian to end of
Ordovician).
Unit:
Hanson Creek Formation
Brachiopods
Sample:
Location:
JL-71
PlPvation 7040 feet, 6300 feet W., 900 feet S., S. W.
oorner Sec. 11, T. 23 N., R. 52 E..
Phragmostrophia merriarni
Atrypa nevadana
Eurekaspirifer pinyonensis
Nucleospira subsphaerica
Age:
Lower Devonian, Emsian, pinyonensis Zone, Interval 10 or
11.
Unit:
Bartine Member, Mc Colley Canyon Formation.
Sample:
JL-73
Elevation 6880 feet, 4200 feet W., 1100 feet S., S. W.
corner Sec. 11, T. 23 N., R. 52 E..
Location:
Dalejina sp. 3
meristellid indet. 1
Acrospirifer? sp. 3
PLicoplasia cooperi 9
Lower Devonian, Spinoplasia Zone, Interval 5 or 6, based
on the Pliooplagia. This Interval occurs in the lowest Kobeh
Member rocks in the Sulphur Spring Range and in the Rabbit Hill
Limestone to the west, i.e., the Monitor Range.
Age:
Unit:
Kobeh Member, Mc Colley Canyon Formation.
94
Sample:
Location:
JL-116
Elevation 6760 feet, 7300 feet W., 800 feet S., N. W.
corner Sec. 23, T. 23 N., R. 52 E..
Anoplia elongata? 2
Meristella sp. 5
A crospirifex sp. 4
(Sample also contained a spiny platycerid gastropod and
rugose coral fragments.)
Age:
Unit:
Lower Devonian, kobehana Zone, Interval 8 or 9.
Kobeh Member, M cC alley Canyon Formation.
Corals
Sample:
Location:
JL-63
Elevation 6520 feet, 3200 feet W., 2700 feet N., S. W.
corner Sec. 35, T. 24 N., R. 52 E..
Emmonsia or Squameofavosites sp
Favosites spp.
Note:
Unit:
None of the favositids can be identified from Flory's thesis
or the published literature. The specimens of E/S are
immature; The F specimens are small fragments. None of
the rugosans are identifiable except by knowing their
source. All of the listed genera are compatible with the
derivation that you indicate.
Kobeh M ember, McCulley Canyon Formation.